1. Field of the Invention
This invention relates to an interiorly partitioned vapor injector, having particular utility for delivery of source reagent vapor mixtures, e.g., comprising one or more precursor reagents in mixture with oxidant, carrier, and/or other reactant or non-reactant species, to a chemical vapor deposition locus, for chemical vapor deposition of selected component(s) of the precursor reagent(s) on a substrate.
2. Background of the Invention
In the practice of chemical vapor deposition (CVD), a source reagent vapor mixture, which may for example comprise one or more precursor reagents in admixture with oxidant and/or carrier species, is delivered to a chemical vapor deposition locus, for chemical vapor deposition of selected component(s) of such precursor reagent(s) on a substrate.
The CVD system for carrying out such deposition may therefore include bubblers, liquid delivery systems, or solid delivery systems for supplying the precursor reagents, which are brought into mixture with oxidant, adjuvant, and/or carrier gases, to provide a source reagent vapor mixture whose composition and whose attendant process conditions (temperature, pressure, flow rate) are critical to the formation and stoichiometry of the film ultimately is deposited on the substrate. The art has described the provision of so-called "showerhead"-type dispersers for the introduction of reagent vapor into CVD reactors. U.S. Pat. No. 5,653,806 issued Aug. 5, 1997. in the name of Peter C. Van Buskirk, describes a showerhead disperser for use in CVD systems and incorporating a heat transfer structure whereby the temperature of the reagent-containing stream being flowed from the outlet of the disperser is controllably maintained at a desired temperature level, for efficient CVD operation. More specifically, the showerhead disperser housing comprises an array of heat exchange passages in the housing wall that are disposed in heat transfer relationship to the source reagent vapor discharge passages in the housing wall, with each of the heat exchange passages being in spaced-apart heat transfer relationship to a multiplicity of source reagent vapor discharge passages in the array of discharge passage openings at the face of the disperser housing.
Such showerhead disperser, while providing for effective thermal control of the dispersed source reagent-containing stream being flowed to the CVD reactor, does not fully satisfactorily accommodate the need for extremely high uniformity of concentration and flow rate in the dispersed gas discharged from the disperser.
In many CVD applications, any significant non-uniformity in the gas stream, either of a compositional character (such that significant gradients of composition are created in the discharged gas stream) or of a flow rate character (such that significant flow velocity gradients are created in the discharged gas stream) will result in wholly unsatisfactory operation and inferior deposited films on the substrate being coated with the desired components of the source reagent vapor. Further, the mixing of the precursor components with an oxidizer, carrier gas, or other components in the disperser housing must be highly efficient, to avoid such localized variation in the composition and flow rate of the gas stream being discharged from the disperser.
Thus, the stoichiometry of the deposited film in the CVD system typically must be rigorously controlled for the manufacture of thin film layers of proper composition, and high uniformity of the thickness of the deposited film is generally desired and necessary. If the deposited material film deviates from the desired stoichiometry and/or thickness uniformity requirements, the resulting article formed from the film, e.g., a microelectric device such as a dynamic random access memory, may be deficient or even useless for its intended purpose.
By way of further specific background, there are a number of issues associated with the mixing of large metal-organic molecules (e.g., Ba(thd), Sr(thd), etc.) with lighter molecules (e.g., oxidizers, O.sub.2, N.sub.2 O, O.sub.3, etc., or sulfur sources, such as H.sub.2 S, etc.) which are used for the chemical vapor deposition of thin films of high-dielectric constant, ferroelectric, and related materials. In the mixing region of the chemical vapor deposition reactor:
(1) the gases and walls of the reactor must be maintained at a constant temperature above the condensation temperature but below the molecular decomposition temperature; PA0 (2) all mixing between different reagents, such as oxidizers (O.sub.2 and N.sub.2 O) and the metal precursors, such as Ba(thd).sub.2, needs to take place in a low pressure region so as to reduce the probability of gas-phase reactions; and PA0 (3) all of the gas components must mix completely to form a homogeneous concentration at the surface of the gas injector to the chemical vapor deposition reactor, which may for example comprise a showerhead-type injector. Variations in reactant concentration across the injector will lead to the deposition of non-uniform film thickness and composition across the substrate.
There is, correspondingly, a need in the art for an improved showerhead-type disperser for the controlled discharge of source reagent-containing vapor streams for CVD and other vapor deposition applications.